In the discussion about the gas levy, SPD chairman Lars Klingbeil spoke out in favor of reviewing the controversial instrument.
"I support the path that Robert Habeck suggested here," Klingbeil told the editorial network Germany with a view to the planned nationalization of the gas importer Uniper.
"But I also want to make it clear: the gas surcharge now needs to be put to the test."
Never before has a federal government had to make so many serious decisions from day one, said Klingbeil.
"In such a situation, a government also needs the strength to reconsider and correct paths." That has now happened with the state's entry into Uniper - it has turned out that this is the better way.
According to the party leader, there were concerns in the SPD about the instrument of the gas levy from the outset.
The goal behind it is and remains correct: "It's about supporting the gas supply infrastructure." But it has to be fair.
Economics Minister Habeck (Greens) announced on Wednesday that the gas levy would be subject to a constitutional review.
His cabinet colleague and Finance Minister Christian Lindner promptly contradicted him.
"There is no further examination, it is closed," he told journalists.
The gas surcharge is intended to support gas importers who have very high replacement procurement costs due to a lack of Russian supplies.
Despite the planned nationalization of Uniper, the federal government wants to stick to the instrument, which is to be introduced on October 1, for the time being.
Habeck had announced changes to the Energy Security Act on Thursday in order to exclude so-called free riders from the levy.
Only companies that are actually in need should benefit from this.
According to the ministry, the changes are to be decided by the cabinet on September 28.